Study on the mechanochemical oxidation of ilmenite

The oxidation kinetics and mechanism of ilmenite milled in air and oxygen atmospheres were investigated. Effects of mill spin rate, milling ball/ore mass ratio and oxygen pressure on the oxidation were examined. The results showed that the former two parameters significantly affected the oxidation process while the influence of oxygen pressure was demonstrated only in a low initial O2 pressure range. An evident O2 adsorption (macro-adsorption) was observed at high O2 pressures (≥50 kPa) but it disappeared with decreasing of O2 pressure. The oxidation was mechanochemically limited at the initial O2 pressures from 152.0 to 33.4 kPa. With further decreasing of the O2 pressure to ≤27.4 kPa, the oxidation changed to be controlled by the O2 adsorption on the active sites of ilmenite particles surface (micro-adsorption). The mechanochemical oxidation occurred mainly at those active sites with the c-axis lattice strain. The mechanism of the oxidation was suggested, upon which a rate equation in kinetic regime was built and derived as follows:−d(1−a)dt=2.1×10−5R2.044ac2.616(1−α)2when t > 0.5 h and FeTiO3 oxidation extent α ≤ 85%. Beyond the extent, the oxidation was limited by O2 diffusion through the solid products layer.